Nikolenko A. Powdery mildew of sugar beet and measures for its control in the central Forest-Steppe of Ukraine.

The thesis is devoted to the study of the biological characteristics of the pathogen powdery mildew of sugar beet fungus Erysiphe communis Grev. f. betae Poteb., distribution, dynamics of the disease and improving the system of crop protection under conditions of the central Forest-Steppe of Ukraine. Based on the analysis of data on disease emergence and dynamics of her growth it is proved, that renewal of powdery mildew during the growing season is in seed plants of sugar beet by establishing favourable temperature to form a ascospores in cleistocarps (+5 to +25° C), the incubation period lasts on average 7-15 days. During the growing season is infecting with disease new plants due to the formation of many generations of conidia that are carried by air currents. Established that conidia germinate best at a temperature of + 25° C and relative humidity of 90-100 %. It is shown that the strong affection to diseases of sugar beet plants with powdery mildew decreases their productivity by 9,3-15,9 t/ha, sugar content - 0,5-0,8 % sugars yield losses are 1,9-3,0 t/ha. It was established, that the prevalence of sugar beet seed plants with powdery mildew affects the quality of seeds - laboratory germination reduced by an average of 18,5 %, weight of 1000 seeds - at 2,2 g. It was studied the effect of the pathogen on a plant sugar beets and found that powdery mildew infestation leads to changes in the intensity of respiration in leaves and reduction of chlorophyll a and b. Defined technical and economic efficiency of fungicides chemical origin against on disease. It was defined optimal time for spraying with fungicides and evaluated the cost-effectiveness of their application.